1. Field of the Invention
The present invention relates to a semiconductor device with semiconductor elements multilayered.
2. Description of the Related Art
FIG. 5 is a sectional view of a conventional semiconductor device with semiconductor elements multilayered, as described in e.g. JP-A-10-242,381. In FIG. 5, reference numerals 1 and 2 denote a semiconductor element, respectively, and reference numeral 3 denotes one of bumps formed on the semiconductor element 1. The semiconductor element 1 is electrically connected to the semiconductor element 2 through an adhesive layer containing conductive particles. The adhesive layer 4 is a single layer of a single material. The adhesive layer 4 is connected to external leads 5 each of which is shaped in a Gull-Wing to constitute an external terminal. Reference numeral 6 denotes sealing resin which forms an external shape sealing the entire periphery of the semiconductor elements 1 and 2 and a connecting portion between them and the external leads 5. In this way, a semiconductor device with the plurality of semiconductor elements is constituted.
Now referring to FIGS. 6A and 6B, an explanation will be given of the function of the adhesive layer 4 containing the conductive particles. FIG. 6A is a view before the semiconductor elements 1 and 2 are bonded, and FIG. 6B is a view after they are bonded. Reference numeral 8 denotes one of conductive particles scattered in the adhesive layer 4. The adhesive layer 4 is essentially an insulator. However, as shown in FIG. 6B, the bump 3 provided on the semiconductor element 1 is pressed against the adhesive layer 4 so that the conductive particles 8 are brought into contact with each other between the bump 3 and the electrode 7 formed on the semiconductor element 2. Thus, electrical conduction is established between the bump 3 and the electrode 7.
The conventional semiconductor device with a plurality of semiconductor elements multi-layered has a problem that because its entirety is sealed, the package is difficult to be low-profiled and cannot provide high heat dissipation. In addition, the semiconductor device is difficult to be miniaturized because the leads constitute external terminals. Further, since the external terminal is extended through the single adhesive material, it cannot give a high degree of electric freedom where both semiconductor elements 1 and 2 are active elements. Moreover, since the bumps must be formed, it is difficult to manufacture the semiconductor device at low cost.